U.S. Pat. No. 5,934,719 has disclosed an external lock assembly for sliding door or window panels comprising a body member fixedly mounted onto a vertically extending side of the sliding sash and a tubular bolt receiving member fixedly mounted onto an opposing vertically extending frame member, wherein the body member is an elongate Π-section profile member, rectilinear channels being defined along the interior elongate lateral sides of the Π-section profile member, locking mechanisms comprising sliding bolt carriage handle members and cooperating guide blocks inserted through the ends of the Π-section profile member and adapted to slide within the rectilinear channels thereof, a pair of coaxially aligned tubular members with an intermediate gap extending at one elongate side of the Π-section profile member, said coaxially aligned tubular members being adapted to receive the bolt locking members of the sliding bolt carriage handle members and said intermediate gap being configured to receive the tubular receiving member that is mounted onto the vertically extending frame member when the vertically extending side of the sliding sash is brought in abutment with the vertically extending frame member whereby the tubular receiving member is coaxially aligned with the pair of coaxially aligned tubular members of the Π-section profile member and, consequent to a sliding of the sliding bolt carriage handle members, a locked condition of the lock assembly is being attained as the bolt locking members are inserted within this tubular receiving member. The lock assembly disclosed in U.S. Pat. No. 5,934,719 has provided a secure locking performance and it has further provided a reliable solution for mounting within the limited space available in between a pair of sliding door panels, as the case is with door or window assemblies comprising one glass and one shutter panel.
The application of the lock assembly disclosed in U.S. Pat. No. 5,934,719 has averted burglary, since it has proved very difficult to violate this lock assembly using coventional burglary tools, such as crowbars. Thus, burglars have been forced to seek new imaginative burglary methods and one of these methods is the cutting of a portion of the sliding sash profile in order to gain access in the interior and attempt to slide to a releasing condition the pair of locking bolts used in the lock assembly. Whilst the time that the burglar needs to spend in order to perform this process already deters him from selecting to violate a door/window locked with this lock assembly comprising the pair of locking bolt members, it is yet important to provide improvements in this type of lock assembly that would avert burglary attempts through applying the abovementioned process of cutting of a portion of the sliding sash profile in order to gain access in the interior.
With a scope of realizing the abovementioned improvement, the present invention proposes the provision of a device adapted to perform immobilization of at least one of the locking bolts of the external lock assembly at the locked position and of a key implement adapted to initiate such immobilization and release, thereby providing an enhanced security of the external lock assembly of the invention, since even if a burglar cuts through the sash and attempts to enter a hand in an interior position facing the lock assembly it will prove yet difficult and by all means an extra time consuming process to manage to drive a key or other appropriate implement (screwdriver, knife or lamina) through the slot provided for the introduction of the specific to this operation key implement and given the limited space in between a pair of sliding door panels it will also be extremely inconvenient, if not impossible, to orient the key or other implement perpendicularly into the slot, i.e. at the orientation required for effecting an appropriate operation thereof.
It is therefore evident that the security offered by the lock assembly of the invention is thus enhanced.
It should further be noted that the employment of the device adapted to perform immobilization of at least one of the locking bolts of the external lock assembly at the locked position and of a key implement effecting the immobilization and release is also critically important for averting unathorized unlocking of the lock assembly by young children or elderly suffering from dementia and related diseases.